Depends on if there are romance options. I'm male, and I generally prefer to play as a female character for aesthetic reasons, because I generally don't like how men look. Also, I generally prefer female names to male names, for whatever reason. However, playing as a girl in games with romance options makes it a bit... awkward. I'm not attracted to males in the slightest, and romancing one, no matter what kind of person they might be and what kind of character I'm playing, is out of the question. But if there's no romance, or the romance is a totally skippable thing, then hell yeah, I'm being the girl.
Even in games where the player characters are actually characters, such as JRPGs or fighting games, I lean toward playing as a girl, though if I prefer a guy's play style, I'll play as him, instead; I don't put aesthetics over practicality and enjoyment.